Hi Grant.

This one is likely a bit tricky. I'm not personally aware of a built-in solution. A Workflow solution is probably best and likely involves some short SDK scripting. You can get started by using Advanced Search Syntax to locate all the annotations created by this user. See page 39 of the attached PDF.

{LF:AnnCreator= “creator”}
Alternatively,
{LFANN:Creator= “creator”}
creator is the user who created the annotation. Note: The only valid format for searching for entries created by a Windows-authenticated user is: “domain\user” You can search for Windows-authenticated users across all domains with \user.
To search for annotations created by Jeff:
{LF:AnnCreator=“Jeff”}

Then, on each entry, for each annotation created by this user, use the SDK Script activity to set the boolean "IsPrivate" and "IsProtected" annotation properties to 0.

Best of luck,
Sam